Treatment of hydrocarbons Containing Sulfides

ABSTRACT

Potassium formate is used together with a sulfide scavenger to remove and otherwise treat sulfhydryl compounds such as hydrogen sulfide present in hydrocarbons and aqueous substrates

RELATED APPLICATION

[0001] This application claims the full benefit of Provisional Application 60/286,715 filed Apr. 25, 2001, which is incorporated herein by reference.

TECHNICAL FIELD

[0002] This invention relates to compositions and methods for the removal or other treatment of hydrogen sulfide and other sulfides present in other compositions. It is particularly useful for the removal of sulfides from hydrocarbons, particularly oil and gas newly recovered from the earth.

BACKGROUND OF THE INVENTION

[0003] Various compositions have been proposed and used for the treatment of hydrocarbons to remove or otherwise treat hydrogen sulfide and/or other sulfides present in them. See, for example, Gatlin's U.S. Pat. Nos. 5,128,049, 5,486,605, 5,488,103, and 5,498,707, U.S. Pat. No. 4,978,512 in the name of Dillon, and Stanchem's Canadian Patent 2,269,476.

[0004] The treating agents may be referred to as scavengers or sulfide scavengers in the patent literature. Frequently they are reaction products of aldehydes and amine compounds, and may or may not contain one or more triazines or derivatives thereof. See the descriptions in columns 5-8 of Trauffler et al U.S. Pat. No. 5,698,171, Sullivan III et al U.S. Pat. Nos. 5,674,377, 5,674,377 and 5,744,024, Rivers et al U.S. Pat. No. 5,554,591, Weers et al U.S. Pat. Nos. 5,223,127, 6,024,866 and 5,284,576, Pounds et al U.S. Pat. Nos. 5,462,721 and 5,688,478, and Callaway U.S. Pat. No. 5,958,352. They may be contacted with the hydrocarbons in various ways as mentioned in these patents and others such as Galloway U.S. Pat. No. 5,405,591 and Fisher U.S. Pat. No. 6,136,282. All of the patents identified in this paragraph and the preceding one are incorporated entirely by reference, as our invention may include the use of any of the sulfide scavengers recited or identified in them, particularly those containing at least one nitrogen.

[0005] As reviewed by Trauffer in U.S. Pat. No. 5,698,171, a product of a reaction between an aldehyde and a nitrogen compound may be used as a scavenging composition. Further, he relates that U.S. Pat. No. 2,776,870 discloses that aqueous amines and alkanolamines are useful for removing acids from a gaseous mixture. Hydrogen sulfide may be selectively removed from gas streams containing carbon dioxide by use of triethanolamine or methyldiethanolamine. British Published Patent Specification No. 2103645 discloses that hydrogen sulfide and carbon dioxide may be removed from a gas mixture by contacting the mixture with a solvent comprising a tertiary amine and a physical absorbent. Suitable physical adsorbents include N-methylpyrrolidone and sulfolane. U.S. Pat. No. 4,112,051 discloses a process for removing acidic gases from a gaseous mixture with an amine-solvent liquid absorbent comprising (1) an amine comprised of at least about 50 mole percent of a sterically hindered amine; and (2) a solvent for the amine mixture which is also a physical absorbent for the acid gases. Suitable sterically hindered amines include various piperidine compounds. Suitable solvents include sulfones and pyrrolidone and piperidone compounds, to name a few. U.S. Pat. No. 4,978,512 discloses methods for reducing the levels of hydrogen sulfide and organic sulfides in a hydrocarbon stream by contacting the stream with a composition comprising a reaction products of a lower alkanolamine with a lower aldehyde. Suitable reaction products include mixtures of triazine and bisoxazolidine compounds. U.S. Pat. No. 4,647,397 discloses a process and composition for removing hydrogen sulfide and similar sulfides from a gas stream. The gas stream is contacted with a substituted aromatic nitrile having an electron-attracting substitutent on the aromatic ring at least as strong as halogen and an organic tertiary amine in an inert organic solvent, such as N-methyl-2-pyrrolidone. The spent contacting solution may be regenerated by heating the solution above the decomposition temperature of the reaction products to separate the sulfides from the liquid phase absorbent solution. U.S. Pat. No. 4,775,519 discloses a continuous process for removing acid gas components from a gas stream by counter-currently contacting the stream with an aqueous solution of a mixture of N-methyldiethanolamine (MDEA) with imidazole or a methyl substituted imidazole. The gas is de-absorbed from the MDEA and the imidazole by reducing the pressure and causing the gas to flash. U.S. Pat. No. 4,624,838 discloses a process for removing acid gases from a gaseous stream by contacting the stream with an aqueous scrubbing solution containing a hetero nitrogen compound comprising either a five- or six- membered ring having a pKa no greater than about 8. Preferred hetero nitrogen compounds include imidazole and piperazine compounds. U.S. Pat. No. 5,347,003 describes a regenerative method where an N—C—N compound is regenerated from a product of a sulfur scavenging reaction, in which said N—C—N compound removes a sulfur atom from a sulfur compound to form the original N—C—N compound. U.S. Pat. No. 3,622,273 discloses a regenerative method for the removal of hydrogen sulfide from a gaseous stream wherein the gaseous stream is contacted with a solution containing, by weight, from 0.005 to 20 percent of a ferric ion complex, from 25.0 to 99.945 percent of water and from 0.05 to 10.0 percent of a buffering agent selected from the group consisting of alkali metal carbonate.

[0006] Trauffer's review continues: There are numerous patents dealing with the removal of hydrogen sulfide from liquid or gas streams with various metal chelates through redox reactions with a higher oxidation state of the metal followed by oxidative regeneration through the use of air. As a sampling: U.S. Pat. No. 4,076,621 deals with iron chelates for the removal of hydrogen sulfide from water; U.S. Pat. No. 4,414,194 deals with iron chelates with alcohol as a crystal modifier; U.S. Pat. No. 4,436,714 deals with the use of metal chelates followed by electrolytic regeneration. All of the patents involving metal chelates describe the use of the metal ion to directly oxidize hydrogen sulfide to a higher oxidation state in common.

[0007] Trauffer's composition includes a scavenging compound which is a reaction product of an aldehyde and an nitrogen compound. Typical aldehydes include formaldehyde, paraformaldehyde, glyoxal, acetaldehyde, butyraldehyde, benzaldehyde, N-(2-hydroxyethyl)dioxazine and oleylaldehyde, while typical amines include methylamine, ethylamine, propylamine, isopropyl amine, oleylamine, ethylene diamine, diethylene tdamine, dimethylamine, diethylamine, monoethanolamine, diethanolamine, morpholine piperazine, thiomonoethanolamine and chlorooleylamine.

[0008] Trauffer's sulfur scavenging compound is represented by a nitrogen compound of the formula R¹R²NCHR³NR⁴R⁵ where each of R¹, R², R³ R⁴ and R⁵ is independently selected from the group consisting of: (i) hydrogen; (ii) a substituted or unsubstituted, saturated or unsaturated, linear, branched or cyclic hydrocarbon chain of 1 to 20 carbons; (iii) a substituted or unsubstituted, saturated or unsaturated, linear, branched or cyclic hydrocarbon chain of 1 to 20 carbons comprising at least one heteroatom selected from the group consisting of nitrogen, oxygen, sulfur and halogen; (iv) a substituted or unsubstituted polymeric chain; and (v) a direct bond to any other of R¹, R², R³ R⁴ and R⁵. Examples of Trauffer's suggested scavenging compounds include various triazines, such as 1,3,5-tris(2-hydroxyethyl)hexahydro-s-triazine, and trimethyl triazine, bisoxazolidines, such as N,N′-methylene bisoxazolidine, piperidines, piperazines, amines, such as methyldiethanolamine, bis(dibutylamino)methane and bis(di-2-hydroxyethylamino)methane, bis(morpholino)methane, and primary, secondary and tertiary amines.

[0009] Trauffer further describes scavenging compounds as a reaction products between (a) an aldehyde of formula HCOR where R is selected from the group consisting of: (i) hydrogen; (ii) a substituted or unsubstituted, saturated or unsaturated, linear, branched or cyclic hydrocarbon chain of 1 to 50 carbons; (iii) a substituted or unsubstituted, saturated or unsaturated, linear, branched or cyclic hydrocarbon chain of 1 to 50 carbons comprising at least one heteroatom selected from the group consisting of nitrogen, oxygen, sulfur and halogen; (iv) a substituted or unsubstituted polymeric chain; (v) a substituted or unsubstituted dimer (vi) a mono or polyaldehyde. The aldehyde may be utilized in anhydrous or hydrated forms of the above. Examples of suitable aldehydes include, but are not limited to: formaldehyde, paraformaldehyde, glyoxal, acetaldehyde,butyraldehyde, benzaldehyde, N-(2-hydroxyethyl)dioxazine, oleylaldehyde and (b) an nitrogen compound of formula HNR⁶R⁷ wherein R⁶ and R⁷ are independently selected from the group consisting of: (i) hydrogen; (ii) a substituted of unsubstituted, saturated of unsaturated, linear, branched or cyclic hydrocarbon chain of 1 to 50 carbons; (iii) a substituted or unsubstituted, saturated or unsaturated, linear, branched or cyclic hydrocarbon chain of 1 to 50 carbons comprising at least one heteroatom selected from the group consisting of nitrogen, oxygen, sulfur and halogen; (iv) a substituted or unsubstituted polymeric chain; and (v) a direct bond to any other of R⁶ and R⁷. Examples of suitable nitrogen compounds include, but are not limited to methylamine, ethylamine, propylamine, isopropyl amine, oleylamine, ethylene diamine, diethylene triamine, dimethylamine, diethylamine, monoethanolamine, diethanolamine, morpholine, piperazine, thiomonoethanolamine, chlorooleylamine.

[0010] The nitrogen compound and the aldehyde of Trauffer's discloure may be reacted in any molar ratio with a preferred ratio being from 1 mole aldehyde to 10 moles nitrogen compound to 10 moles aldehyde to 1 mole nitrogen compound, a more preferred ratio being from 1 mole aldehyde to 5 moles nitrogen compound to 5 moles aldehyde to 1 mole nitrogen compound, an even more preferred ratio being 1 mole aldehyde to 3 moles nitrogen compound to 3 moles aldehyde to 1 mole nitrogen compound and a most preferred ratio being 1 mole aldehyde to 1 mole nitrogen compound. The scavenging compound formed from the reaction of the aldehyde and nitrogen compound are dependent upon the selected nitrogen compound, the selected aldehyde and the ratios of each selected. Similarly mixtures of the above aldehydes and nitrogen compounds may also be reacted in order to form singular or mixtures of various scavenging compounds. The reaction of the nitrogen compound and the aldehyde listed above will typically result in the formation of an aminal. Aminals typical of those formed in the described reaction are of the type R¹R²NCHR³NR⁴R⁵, R¹N═CR²R³ and/or R¹R²NCR³R⁴OH where n is an integer from 1 to 1000 and each of R¹, R², R³ R⁴ and R⁵ is independently selected from the group consisting of: (i) hydrogen; (ii) a substituted of unsubstituted, saturated of unsaturated, linear, branched or cyclic hydrocarbon chain of 1 to 20 carbons; (iii) a substituted or unsubstituted, saturated or unsaturated, linear, branched or cyclic hydrocarbon chain of 1 to 20 carbons comprising at least one heteroatom selected from the group consisting of nitrogen, oxygen, sulfur and halogen; (iv) a substituted or unsubstituted polymeric chain; and (v) a direct bond to any other of R¹, R², R³ R⁴ and R⁵. Examples of scavenging compounds which are useful in scavenging include various triazines, such as 1,3,5-tris(2-hydroxyethyl)hexahydro-s-triazine, and trimethyl triazine, bisoxazolidines, such as N,N′-methylene bisoxazolidine, piperidines, piperazines, amines, such as methyldiethanolamine, bis(dibutylamino)methane and bis(di-2-hydroxyethylamino)methane, bis(morpholino)methane, primary, secondary and tertiary amines, non-generic aminals such as 2,7-dioxa-5,10 diazabicyclo[4.4.0]dodecane, methylaminomethanol, ethylmethyleneimine, isopropylmethyleneamine.

[0011] Gatlin, in U.S. Pat. No. 5,128,049, reviews the prior art partially as follows: In U.S. Pat. No. 4,569,766, a method is disclosed for scavenging hydrogen sulfide and mercaptans from fluids by contacting the fluids with maleimides. In U.S. Pat. No. 4,680,127, a method is disclosed for reducing the amount of hydrogen sulfide in aqueous or wet gaseous mediums by adding an effective amount of glyoxal, preferably in combination with formaldehyde or glutaraldehyde. In U.S. Pat. No. 4,748,011, a method is disclosed for the separation and collection of natural gas comprising the use of a sweetening solution. The sweetening solution consists of an aldehyde or a ketone, methanol, an amine inhibitor, sodium or potassium hydroxides and isopropanol. The amine inhibitor includes alkanolamines to adjust the pH. In U.S. Pat. No. 4,978,512, a method is disclosed for selectively reducing the levels of hydrogen sulfide and organic sulfides present in gaseous or liquid hydrocarbon streams or mixtures thereof by contacting the streams with the reaction product of a lower alkanolamine and a lower aldehyde.

[0012] Gatlin goes on to disclose a two-step scavenging process utilizing scavenging agents such as hexahydro-1,3,5-tris (2-hydroxyethyl)-S-triazine; tris (hydroxymethyl) nitromethane; a mixture of 4-(2-nitrobutyl)morpholine and 4,4′-(2-ethyl-2-nitrotrimethylene)-dimorpholine; a mixture of 4,4-dimethyloxazolidine and 3,4,4-trimethyloxazolidine; hexahydro-1,3,5-triethyl-S-triazine; a mixture of sodium 2-pyridinethiol-1-oxide and hexahydro-1,3,5-tris(2-hydroxyethyl)-S-triazine; 2,2-dibromo-3-nitrilopropionamide; methanol [[[2-(dihydro-5-methyl-3(2H)-oxazolyl)-1-methylethyoxy]methoxy]methoxy]; 2[(hydroxymethyl)amino]ethanol; 2[(hydroxymethyl)amino]-2-methyl-propanol; sodium dichloro-S-triazinetrione dihydrate; or a solution of 1,3-bis(hydroxymethyl)-5,5-dimethylhydantoin and 1-(hydroxymethyl)-5,5-dimethylhydantoin. Further, Gatlin reminds us that hexahydro-1,3,5-tris (2-hydroxyethyl)-S-triazine is commercially available in aqueous solution from United Industrial Chemicals, Inc. under the tradename UNICIDE TZ-135 and from Angus Chemical Company under the tradename BIOBAN GK. UNICIDE TZ-135 is marketed as a fungicide and bactericide for use, by way of example, in controlling the growth of bacteria and fungi in oil well drilling and processing fluids. BIOBAN GK is also marketed as a bactericide; tris (hydroxymethyl) nitromethane is commercially available in aqueous solution from Angus Chemical Company under the tradename TRIS NITRO, and is marketed as an antimicrobial agent; a mixture of 4-(2-nitrobutyl)morpholine and 4,4′-(2-ethyl-2-nitrotrimethylene)-dimorpholine is commercially available from Angus Chemical Company under the tradenames BIOBAN P-1487 or BIOBAN FP, and is marketed as an antimicrobial agent; a mixture of 4,4-dimethyloxazolidine and 3,4,4-trimethyloxazolidine is commercially available from Angus Chemical Company under the tradename BIOBAN CS-1135, and is marketed as antimicrobial agent for use in oilfield water systems, and as a corrosion inhibitor. This material is also available from Cosan Chemical Corporation under the tradename COSAN 101; hexahydro-1,3,5-triethyl-S-triazine is commercially available from R. T. Vanderbilt Co., Inc. under the tradename VANICIDE TH, and is marketed as an industrial preservative; a mixture of sodium 2-pyridinethiol-1-oxide and hexahydro-1,3,5-tris(2-hydroxyethyl)-S-triazine is commercially available from Olin Chemicals under the tradename TRIADINE 10, and is marketed as an antimicrobial agent; 2,2-dibromo-3-nitrilopropionamide is commercially available from Dow Chemical U.S.A. under the tradename DBNPA, and is marketed as a broad spectrum, low persistency biocide; methanol [[[2-(dihydro-5-methyl-3(2H)-oxazolyl)-1-methylethyoxy]methoxy]methoxy] is commercially a in aqueous solution from Cosan Chemical Corporation under the tradename Cosan 145, and is marketed as an antimicrobial preservative; 2-[(hydroxymethyl)amino]ethanol is commercially available from Troy Chemical Corp. under the tradename TROYSAN 174, and is marketed as a water-soluble biocide. This material is also available from Cosan Chemical Corporation under the tradename COSAN 91; 2[(hydroxymethyl)amino]-2-methyl-propanol is commercially available from Troy Chemical Company under the tradename TROYSAN 192, and is marketed as a water-soluble biocide. Sodium dichloro-S-triazinetrione dihydrate is commercially available from Olin Chemicals under the tradename OCI 56, and is market for use as a bleach, sanitizer or cleaning compound. Solutions of 1,3-bis(hydroxymethyl)-5,5-dimethylhydantoin, antibacterial preservatives, may also be used as scavenging agents. Gatlin prefers to use dilute solutions of the materials described above as scavenging agents in compositions containing from about 1 to about 50 percent, and typically from about 10 to about 30 percent, of one or more of the preferred active ingredients identified above. These dilute solutions of scavenging agents are preferably added to the hydrogen sulfide-containing streams at concentrations of about 0.05 to about 100 ppm of diluted scavenging agent per 1 ppm of hydrogen sulfide, and most preferably, at concentrations of from about 2 to about 10 ppm of diluted scavenging agent per 1 ppm of hydrogen sulfide.

[0013] Weers et al, in U.S. Pat. No. 6,024,866, utilize a hydrogen sulfide scavenger prepared by reacting an alkylenepolyamine with formaldehyde. They remind us that the use of various aldehydes which react with hydrogen sulfide has been known in the prior art for some time. For example, U.S. Pat. No. 2,426,318 discloses a method of inhibiting the corrosive action of natural gas and oil containing soluble sulfides on metals by utilizing certain aldehydes, preferably formaldehyde. Depending on the size of the alkylene moiety, the scavenger can be water soluble and/or petroleum hydrocarbon soluble. Having both water solubility and oil solubility can be advantageous in many case.

[0014] The hydrogen sulfide scavengers of the Weers et al disclosure (U.S. Pat. No. 6,024,866) are prepared by reacting alkylenepolyamines and formaldehyde in a known manner. Where water is present, the alkylenepolyamine is selected so that the reaction product is preferably soluble both in water and hydrocarbon stock. The polyamines useful in the preparation of the hydrogen sulfide scavengers useful in the method of the Weers invention are alkylenepolyamines represented by the formula H₂NRNH(RNH)_(x)H wherein each R is independently an alkylene radical having 2 to about 20 carbon atoms and x is 0 to about 15. The alkylene radical may be straight or branched chain, e.g., ethylene, methylethylene, trimethylene, phenylethylene and may be substituted with one or more organic or inorganic radicals that do not react with formaldehyde, e.g., halo such as chloro, bromo, fluoro, alkyloxy, etc. As a practical matter, however, the alkylene radical is preferably a straight chain lower alkylene, e.g., ethylene or propylene and any suitable lower alkyl substituent thereon, such as methyl, ethyl, etc. Where water solubility of the scavenger is of lesser importance, the alkylene radical of the polyamine may be derived from fatty materials, such as tallow. Representative polyamines include ethylenediamine, propylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, tetrabutylenepentamine, hexaethyleneheptamine, hexapentyleneheptamine, heptaethyleneoctamine, octaethylenenonamine, nonaethylenedecamine, decaethyleneundecamine, decahexyleneundecamine, undecaethylenedodecamine, dodecaethylenetridecamine, tridecaethylenetetradecamine, N-tallow propylenediamine and higher polyamines. In general, the scavenging compounds of the Weers et al 6.024.866 disclosure are prepared by the exothermic reaction of an alkylenepolyamine, e.g., diethylenediamine, and formaldehyde. The mole ratio of polyamine to formaldehyde may range from about 1:1 to about 1:14, preferably about 1:1 to about 1:3. The reaction temperature is maintained at about 50°-60° C. The reaction may occur over a period of approximately an hour at a time. A temperature drop indicates the completion of the reaction. The resulting reaction product is a complex mixture of compounds, including, for example, methylene-bridged diethylenetriamines.

[0015] In U.S. Pat. No. 5,958,352, Callaway et al propose the use of aldehyde ammonia trimers as scavengers for sulfhydryl compounds in natural gas. The scavenging agents of the Callaway invention are aldehyde ammonia trimers that generally have the following formula:

[0016] wherein R¹, R², and R³ are independently selected from the group consisting of hydrogen and hydrocarbon groups having between about 1-8 carbon atoms, selected from the group consisting of straight, branched, and cyclic alkyl groups, aryl, alkaryl, and aralkyl groups, and heterocyclic alkyls containing oxygen or tertiary nitrogen as a ring constituent wherein none of R¹, R², or R³ is an alkoxyalkylene substitutent. In a preferred embodiment, R¹, R², and R³ are methyl groups. Aldehyde ammonia trimers may be manufactured by reacting acetaldehyde with aqueous ammonia in a 1:1 molar ratio. Water or another solvent, such as methanol, can be used in the reaction to prevent solid trimer from precipitating out of the solution. The amount of water used may vary depending upon how the product will be used. For example, if the substrate will be hydrophobic, e.g., a dry oil phase, the trimer may be formulated in isopropanol rather than water. In the field, the trimer preferably should be used in a solution having an active concentration of about 2-30%, preferably about 10-20%.

[0017] Galloway, in U.S. Pat. No. 5.405,591, proposes scavenging with a triazine, which is a reaction product of an alkanolamine and an aldehyde. The triazine extracts sulphide(s) from sour gas to sweeten the gas by reacting with the sulphide(s) to form a solution comprised of a sulphonated component and an alkanolamine component, which substantially separates the sulphonated component from the alkanolamine component. More aldehyde can be added to the alkanolamine component to form additional sulphide reactive agent. In this way, a cyclic, regenerative process is provided. The make-up triazine can be produced from any of the following alkanolamines: mono, di, and tri methly amine; mono, di and tri ethyl amine; mono di, and tri n-propyl amine; iso proply amine; n, iso, sec, and tert butyl amine and ethylenediamine. The make-up triazine can be produced from any of the following aldehydes: formaldehyde (methanal); acetaldehyde (ethanal); propinaldehyde (propanal); and n-butyalaldehyde (butanal).

[0018] In U.S. Pat. No. 5,554,349, Rivers, et al propose the use of a mixture of amines made by reacting an amine compound with an aldehyde compound to reduce the levels of H2S in liquid or gaseous hydrocarbon streams. At least one of the compounds must have an alkoxyalkylene radical. The reaction products are trizines having substituent groups independently selected from hydrogen and an alkyl radical, including substituted alkyl radicals, of 1 to 5 carbon atoms; where at least one of the groups is an alkoxyalkylene group. In another embodiment of the invention, the amine mixture may contain other byproducts, such as the monomers which make up the hexahydrotriazine, with or without the hexahydrotriazine being present. These materials are selective to the reduction of H2S levels in hydrocarbon or aqueous streams in the presence of CO2 which does not compromise their performance.

[0019] Amine compounds or reactants proposed by Rivers et al include, but are not necessarily limited to, 3-methoxypropylamine (CH3OCH2CH2CH2NH2; sometimes noted as MOPA); 3-ethoxypropylamine; ammonia (NH3); methylamine (CH3NH2); dimethylamine (CH3NHCH3); 1-methoxyisopropylamine [CH3OCH2CH(NH2)CH3, also known by the product name of Jeffamine Registered TM M-89 amine sold by Texaco Chemical Co.] and mixtures thereof. The amine reactants to aldehyde reactants molar ratio may range from about 10:1 to 1:10. It is preferred that the amine to aldehyde molar ratio be in the range from about 1.2:1 to 1:1.2. The molar ratio of alkoxy-alkyleneamine to all other amines used as reactants may range from about 1:0 to 1:100, preferably from about 1:0 to 1:9.

[0020] It has been further discovered (as related in Rivers et al U.S. Pat. No. 5,554,349) that the addition of a dialdehyde at some point in the process has a beneficial effect. For example, in one embodiment, the amine compound and the aldehyde compound are reacted together in a first step and then the dialdehyde is added in a second step. At the time of writing, it was unclear whether the dialdehyde is reacting to give an unknown product or if the dialdehyde was simply blended with the reaction products of the amine compound and the aldehyde compound. In any event, it was observed that the addition of the dialdehyde gives products with better results for scavenging H2S than when it was absent. Alternatively, the dialdehyde may be added with the monoaldehyde compound in the first step for reaction with the amine compound. In yet another embodiment, in the two-step process, there may be added between the first and second steps the reaction product of a second amine compound and a second aldehyde compound.

[0021] Generally, the second amine compound is different from the first amine compound or the second aldehyde compound is different from the second aldehyde compound, or both. There is no advantage for the second amine compound and second aldehyde compound to be the same as in the first step. Suitable dialdehydes for the enhanced embodiment of the invention include, but are not necessarily limited to, glyoxal; glutaraldehyde; succinic aldehyde; 1,6-hexane dialdehyde (adipic aidehyde) and mixtures thereof. Glyoxal is particularly preferred. Adialdehyde, such as those described above, may be advantageously blended and/or reacted with known triazine H2S scavengers such as . Specifically, the reaction of MEA with CH2O gives 1,3,5-tris-(2-hydroxyethyl)-hexahydro-D-triazine

[0022] In U.S. Pat. No. 5,688,478, Pounds describes a reaction product of an alkanolamine with a C1 to C4 dialdehyde, especially ethanedial, for use as a sulfide scavenger. Certain prior art is reviewed by Pounds: U.S. Pat. No. 4,978,512 in the name of Dillon describes a method for selectively reducing the levels of hydrogen sulfide and organic sulfides from gaseous and/or liquid hydrocarbon streams, particularly natural gas streams, by contacting the streams with the reaction product of an alkanolamine with a monoaldehyde. The patent also discloses that the reaction product may be mixed with a glycol prior to contact with the gas in order to reduce the water levels in the gas. U.S. Pat. No. 5,128,049 (Gatlin) discloses a method of using triazines as hydrogen sulfide scavengers. U.S. Pat. No. 5,169,411 (Weers) discloses a method for preventing liberation of H2S in crude oil or petroleum residuum medium with imines. U.S. Pat. No. 5,266,185 (Weers) discloses the suppression of hydrogen sulfides in a heavy hydrocarbon derived from heavy crude oil by contacting the petroleum with the reaction product of a heterocyclic aldehyde and an organic primary amine. The useful compound was described as an imine. U.S. Pat. No. 5,284,576 (Weers) discloses a process for scavenging hydrogen sulfide using a scavenger prepared by reacting an alkylenepolyamine, including diethylenetriamine, and formaldehyde. U.S. Pat. No. 5,314,672 (Vasil) discloses a method of selectively reducing the levels of hydrogen sulfide and organic sulfides by contacting natural gas with the reaction product of ethylenediamine and 50% uninhibited aqueous formaldehyde.

[0023] Pounds, in the U.S. Pat. No. 5,688,478 discussed above, described a method for selectively reducing the levels of hydrogen sulfide and organic sulfides present in a gas comprising the steps of providing a source of a dialdehyde having two carbonyl groups; providing a source of an alkanolamine having at least one hydrogen atom bonded directly to a nitrogen atom; reacting between about 1.5 and about 3 equivalents of hydrogen atoms bonded directly to a nitrogen atom in the alkanolamine for every equivalent of carbonyl groups in the dialdehyde to form a reaction mixture substantially free of triazines; contacting the sulfides with a scavenger consisting essentially of the reaction mixture, wherein the scavenger is produced at a rate sufficient to reduce the level of sulfides in the gas contacted below a given level, and wherein the scavenger flows directly from the reacting step to the contacting step; separating the gas from the spent composition; and discarding the spent composition. The method requires contacting the particular stream with a composition which is a reaction product of an active primary or secondary amine with an aldehyde. For purposes of the description, an aldehyde included both monoaldehydes (one carbonyl group) and dialdehydes (two carbonyl groups). Pounds' preferred monoaldehydes include, but are not limited to, formaldehyde, acetaldehyde, propionaldehyde (propanal), and n-butyraldehyde (1-butanal). The most preferred monoaldehyde is formaldehyde. The preferred dialdehyde is ethanedial.

[0024] In Gatlin's U.S. Pat. No. 5,486,605, a composition is disclosed that is adapted to convert hydrogen sulfide and organic sulfides to nontoxic polymers. The compositions comprise amine resin solutions made by reacting sterically hindered amines such as amine heads with aldoses selected from the group consisting of D-aldoses having from 3 to 6 carbon atoms. Streams containing hydrogen sulfide or organic sulfides are preferably treated by contacting such streams with from about 2 to about 4 ppm or more of the amine solution of the invention per ppm of sulfide.

[0025] As related by Gatlin, U.S. Pat. No. 4,748,011 discloses a method for the separation and collection of natural gas through use of a sweetening solution comprising an aldehyde or ketone, methanol, an amine inhibitor (including alkanolamines), sodium or potassium hydroxides, and isopropanol. Further, U.S. Pat. No. 4,978,512 discloses a method for selectively reducing the levels of hydrogen sulfide and organic sulfides present in gaseous or liquid hydrocarbon streams or mixtures thereof by contacting the streams with a composition comprising the reaction product of a lower alkanolamine with a lower aldehyde.

[0026] U.S. Pat. No. 4,112,051 discloses the removal of acidic gases, including hydrogen sulfide, from normally gaseous mixtures by contacting the mixtures with an amine-solvent liquid absorbent comprising an amine having at least about 50 mol percent of a sterically hindered amine and a solvent for the amine mixtures which is also a physical absorbent for the acidic gases.

[0027] In Gatlin's U.S. Pat. No. 5,486,605, a hydrogen sulfide or organic sulfide converter is provided that comprises the reaction product of sterically hindered amines such as selected aliphatic diamines, aliphatic triamines, amino alcohols, and mixtures thereof with aldoses. According to one preferred embodiment of the Gatlin U.S. Pat. No. 5,486,605 disclosure, a hydrogen sulfide or organic sulfide converter is provided that comprises the reaction product of amine heads with a second component comprising an aldose selected from the group consisting of D-aldoses having from three to six carbon atoms. According to another preferred embodiment of the Gatlin U.S. Pat. No. 5,486,605 disclosure, a hydrogen sulfide or organic sulfide converter is provided that comprises the reaction product of amine heads with a crude aldose mixture made by reacting formaldehyde, methanol, sodium hydroxide and water. According to another preferred embodiment of the Gatlin U.S. Pat. No. 5,486,605 disclosure, a hydrogen sulfide or organic sulfide converter is made that comprises the reaction product of amine heads with a second component comprising about 70 parts of 37% formaldehyde containing about 7 weight percent methanol and about 30 parts of about 50 weight percent sodium hydroxide in water reacted together slowly while controlling the temperature between about 190° F. and about 210 degrees F., thereafter cooled, and adjusted to a pH of between about 6 and 7 by the slow addition of 30% hydrochloric acid. According to another preferred embodiment of the Gatlin U.S. Pat. No. 5,486,605 disclosure, a hydrogen sulfide or organic sulfide converter is provided that comprises the reaction product of amine heads with an aldose in a system further comprising up to about 90 weight percent of a solvent comprising a lower alcohol. According to another embodiment of the Gatlin U.S. Pat. No. 5,486,605 disclosure, a composition is provided in which the hydrogen sulfide or organic sulfide converter of the invention further comprises a solvent adapted to reduce foaming and prevent cross-linking. Preferred solvents include methanol, methoxymethanol, water, and mixtures thereof. According to another embodiment of the Gatlin U.S. Pat. No. 5,486,605 disclosure, a composition is provided in which the hydrogen sulfide or organic sulfide converter of the invention is diluted with methanol, methoxymethanol, mixtures of methanol and methoxymethanol, or water, and optionally, a minor amount of a surfactant. According to another embodiment of the Gatlin U.S. Pat. No. 5,486,605 disclosure, a method is provided for removing hydrogen sulfide from gaseous and liquid hydrocarbon streams by contacting such streams with a solution comprising a hydrogen sulfide converter (scavenger) of the Gatlin invention as described above.

[0028] Use of the compositions and methods described by Gatlin in U.S. Pat. No. 5,486,605 allows direct conversion of hydrogen sulfide to a stable form without liberating the hydrogen sulfide during regeneration in the manner experienced with prior art compositions and methods. The complexes produced by reacting the compositions disclosed in Gatlin's U.S. Pat. No. 5,486,605 with hydrogen sulfide do not have to be removed from the process fluids for regeneration. The complexes produced thereby are largely water soluble, and are therefore easily separated from gaseous or liquid hydrocarbon streams.

[0029] In U.S. Pat. No. 5,486,605, Gatlin disclosed that compositions which convert hydrogen sulfide or other organic sulfides to water soluble, nontoxic, stable complexes can be made by reacting under controlled conditions solutions of sterically hindered amines comprising amine heads, selected aliphatic diamines, aliphatic triamines, amino alcohols, and mixtures thereof, with aldehydes, aldehyde donors, or the reaction products of lower alkanolamines and lower aldehydes. The complexes thus formed are easily separated from gaseous or liquid hydrocarbons.

[0030] Use of the compositions disclosed in Gatlin's U.S. Pat. No. 5,486,605 is said to be more efficient than using conventional materials, with significantly lower concentrations of the converter being required (such as from about 2 to 3 times less) in actual practice to achieve the same degree of sulfide conversion. Typical application ratios for the Gatlin compositions are from about 2 to about 4 ppm of converter per ppm of hydrogen sulfide in the treated fluid. This improved conversion allows more complete removal of hydrogen sulfide at a minimal cost, often without the need for a scrubber tower, which further reduces related equipment costs.

[0031] Generally speaking, the compositions of Gatlin's U.S. Pat. No. 5,486,605 are preferably made by reacting a solution comprising free aldehyde and the reaction product of a lower aldehyde and a lower alkanolamine either with a solution comprising a sterically hindered amine, preferably amine heads, or with an activator comprising the reaction product of a amine heads and formaldehyde. A particularly preferred lower aldehyde for use in making the subject compositions is formaldehyde. A particularly preferred lower alkanolamine for use in making the subject compositions is monoethanolamine. The term “amine heads” refers to an unrefined mixture of alkyl diamines that comprise from 4 to 6 carbon atoms.

[0032] Examples of alkyl diamines typically found in amine heads include aminomethylcyclopentylamine; 1,2-cyclohexanediamine (1,2-diaminocyclohexane); 1,5-pentanediamine, 2-methyl; 1,6-hexanediamine; 1H-azepine, hexahydro; and 1,4-butanediamine. Amine heads is commercially available from Monsanto Company and DuPont as a byproduct in the manufacture of hexamethylenediamine. Although amine heads is a convenient and useful source of aliphatic diamines suitable for use in making the scavengers of Gatlin's U.S. Pat. No. 5,486,605, it should be understood that other diamines or triamines not present in amine heads can likewise be used within the scope of the invention. Examples of other aliphatic diamines and triamines that can be satisfactorily used include 1,4-diaminocyclohexane and bis-hexamethylenetriamine. One particularly preferred composition is made by reacting amine heads with formaldehyde. Another preferred composition, as described in Gatlin's U.S. Pat. No. 5,486,605, is made by reacting amine heads with a solution of free formaldehyde and the reaction product of monoethanolamine and formaldehyde. Another preferred composition is made by reacting the reaction product of monoethanolamine and formaldehyde with an activator comprising the reaction product of amine heads and formaldehyde. Another composition described by Gatlin in U.S. Pat. No. 5,486,605 comprises the reaction product of amine heads with a formaldehyde donor such as HMTA or hydantoin.

[0033] Other materials believed to be satisfactory for use in place of amine heads include, for example, methyl-diethanolamine; 2-[(hydroxymethyl)amino]ethanol, 2-amino-2-methyl-1-propanol; methylethanol amine; 2-methyl-1-amino ethanol; 2-ethyl-1-amino ethanol; 2-tertiary butylamino ethanol, 2-tertiary butylamino ethanol; 2-amino-2-ethyl-1,3-propanediol; 2-[(hydroxymethyl)amino]-2-methyl propanol; hydantoin; 5,5-dimethyl-1-hydantoin; acetaldehyde ammonia; acetalsoxime; 2-amino-2-hydroxymethanol, 1-3-propanediol; 2-amino-1,3-propanediol; 2-amino-2-methyl-1,3-propanediol; the reaction product of methyl pyrol and hydroxylamine; choline; and amino-spirocyclic borate esters derived by reacting boric acid with glycols, amines and amides.

[0034] Components that may be reacted with sterically hindered amines comprising amine heads, selected aliphatic diamines, aliphatic triamines, or amino alcohols to produce compositions of the Gatlin 5,486,605 patent include, for example, aldehydes, aldehyde donors, the reaction products of lower alkanolamines and lower aldehydes, and the family of D aldoses having from 3 to 6 carbon atoms. Aldehydes believed to be useful for making the subject compositions are preferably selected from the group consisting of monoaldehydes and dialdehydes having from 1 to 6 carbon atoms, and mixtures thereof, with formaldehyde, acetaldehyde, glycolaldehyde, glyceraldehyde, hydroxymethyl glyceraldehyde, glyoxal, and methyl formcel (a hemi-acetal, 55 percent formaldehyde solution in methanol and methoxy-methanol or water) being particularly preferred.

[0035] Aldehyde donors suggested by Gatlin in U.S. Pat. No. 5,486,605 as useful in making scavengers are preferably selected from the group consisting of hydantoin; hexamethylenetetramine; hexamethylolmelamine; 2-[(hydroxymethyl)amino]ethanol; 5,5-dimethylhydantoin; tris(hydroxymethyl)nitromethane; 2-nitro-2-methyl-1-propanol; 2-nitro-2-ethyl-1,3-propanediol; 2-nitro-1-butanol; and acetaldehyde ammonia. D-aldoses having from 3 to 6 carbon atoms also suggested as useful are preferably selected from the group consisting of D-Glyceraldehyde; D-Erythrose; D-Ribose; D-Arabinose; D-Allose; D-Altrose; D-Glucose; D-Mannose; D-Threose; D-Xylose; D-Lyxose; D-Gulose; D-Idose; D-Galactose; D-Talose; and mixtures thereof.

[0036] Additional known or proposed sulfide scavengers are (1) the 1,3,5-hexahydro-1,3,5-tert-butyl triazine of Sullivan III et al U.S. Pat. No. 5,674,377, (2) the mono- and polyamidines of Weers et al in U.S. Pat. No. 5,223,127, and (3) the bisoxazolidines of Rivers in U.S. Pat. No. 6,117,310.

SUMMARY OF THE INVENTION

[0037] Our invention includes (a) compositions comprising potassium formate and a sulfide scavenger and (b) methods of treating sulfide-containing hydrocarbons by contacting them with the compositions comprising potassium formate and a sulfide scavenger. By a sulfide scavenger, we mean any of the compositions described or suggested for sulfide treatment in any of the patents reviewed in the Background of the Invention as well as any other effective sulfide scavenger.

[0038] In addition to hydrocarbons such as newly produced crude oil and natural gas, our invention may be used to treat other hydrocarbon substrates. The term “hydrocarbon substrate” is meant to include unrefined and refined hydrocarbon products, including natural gas, derived from petroleum or from the liquefaction of coal, both of which contain hydrogen sulfide or other sulfur-containing compounds. Thus, particularly for petroleum-based fuels, the term “hydrocarbon substrate” includes wellhead condensate as well as crude oil which may be contained in storage facilities at the producing field. “Hydrocarbon substrate” also includes the same materials transported from those facilities by barges, pipelines, tankers, or trucks to refinery storage tanks, or, alternately, transported directly from the producing facilities through pipelines to the refinery storage tanks. The term “hydrocarbon substrate” also includes refined products, interim and final, produced in a refinery, including distillates such as gasolines, distillate fuels, oils, and residual fuels. As used in the claims, the term “hydrocarbon substrate” also refers to vapors produced by the foregoing materials.

[0039] The scavenging agents of the present invention may be used to treat aqueous and hydrocarbon substrates that are rendered “sour” by the presence of “sulfhydryl compounds,” such as hydrogen sulfide (H2S), organosulfur compounds having a sulfhydryl (—SH) group, known as mercaptans, also known as thiols (R—SH, where R is a hydrocarbon group), thiol carboxylic acids (RCO—SH), dithio acids (RCS—SH), and related compounds. We include hydrogen sulfide in the term “sulfhydryl compound.”

[0040] As used in this application, the term “aqueous substrate” refers to any “sour” aqueous substrate, including waste water streams in transit to or from municipal waste water treatment facilities, tanning facilities, and the like.

[0041] Our invention includes a method of treating sulfides in hydrocarbons, hydrocarbon substrates, or aqueous substrates comprising (a) contacting the hydrocarbons or substrates containing sulfides with potassium formate and (b) contacting the hydrocarbons or substrates containing sulfides with a sulfide scavenger. Contacting of the sulfide-containing hydrocarbon with potassium formate may take place before the scavenger is used, substantially at the same time, or after the scavenger is used. The potassium formate is preferably in an aqueous solution, but need not be. The scavenger may be any effective sulfide scavenger, as the primary mechanism of our invention is that the potassium formate acts to draw water from association with the hydrocarbons, the sulfides being themselves associated with the water. The use of potassium formate, whether or not initially in solution, thus tends to improve the efficiency of the scavenging process more or less regardless of the identity of the particular scavenger.

[0042] Typically, sulfides such as hydrogen sulfide in hydrocarbons tend to associate with whatever water is present with or in contact with the hydrocarbons. Our invention utilizes the hygrosopic nature of the potassium formate to separate the water from the hydrocarbons, which causes the sulfides to come with it, thus increasing the efficiency of the scavenger when contact is made between the scavenger and the sulfide. Potassium formate solutions have the additional advantage of a low freeze point. We are thus able to employ our invention in climates, remote locations, and temperatures where it is normally difficult to employ aqueous solutions.

[0043] Our invention includes compositions comprising combinations of potassium formate and sulfide scavengers, with or without additional potassium hydroxide, and the use of these compositions in sulfide removal from hydrocarbons. In addition, our invention includes the treatment of sewage suspensions, and pulp systems in the paper industry to reduce sulfide emissions. Our novel compositions may be used to treat these and other odiferous materials; also, methods similar to our hydrocarbon-treating methods may be used for sewage, pulp, and other odiferous compositions and systems, i.e. treating with potassium formate and sulfide scavengers in separate steps or at the same time.

DETAILED DESCRIPTION OF TEH INVENTION

[0044] As indicated above, we may use any sulfide scavenger in our process and in our novel compositions including potassium formate. We prefer to use amine/aldehyde condensates, and particularly the hydroxy methyl amino alcohols and other materials described in Gatlin's U.S. Pat. Nos. 5,486,605 and 5,488,103. Our invention may be used with any of these and/or any of the scavengers described in the patents mentioned in the Background of the Invention, all of which are incorporated by reference. Solvents and other materials which may be present with the scavengers include (without intending to be limiting in any way), water, methanol, glycols, and cellosolves.

[0045] The aqueous potassium formate solutions and slurries we use in conjunction with sulfide scavengers may range in potassium fornate concentration from 1% to 99% by weight, but we prefer solutions from 20% to 40%, and most preferably 25-35%. When used prior to the application of the scavenger, they may be contacted with the hydrocarbons by continuous injection or in an adsorption tower. See also the description in Gatlin U.S. Pat. No. 5,128,049 of “pre-treatment” and “polishing” steps (column 3, line 62-column 4, line 36), which are also useful in the present invention. More than one injection or treatment step may be used, and different concentrations of the scavenger and the potassium formate solution may be used in each.

[0046] Where there is sufficient water in association with the hydrocarbons, very high concentrations of potassium formate may be used, and even solid potassium formate can be useful in circumstances where the solid is likely readily to contact the water/sulfide composition. Our invention has the additional advantage that it will depress the freeze point of a prepared solution or mixture and can be readily used under very cold conditions.

[0047] Because of the hygroscopic nature of potassium formate, our process is particularly useful in treating gaseous hydrocarbons, in that it will tend to remove moisture from the gas and/or inhibit the absorption of water by the gaseous hydrocarbons.

[0048] An additional advantage of our process is that the effectiveness of the scavenger is prolonged by the alkalinity of the potassium. The potassium formate content of our treating compositions can be generated in solution by the reaction of formic acid and potassium hydroxide, and this solution can be utilized more or less without additional steps; moreover, the alkalinity of the solution can be enhanced by using an excess of potassium hydroxide for the reaction. Potassium hydroxide can simply be added to an already prepared solution of potassium formate, also resulting in enhanced performance of the scavenger.

[0049] Whether the potassium formate is combined with the scavenger or used separately, useful preferred compositions and ratios (separate or premixed) of the ingredients include:

[0050] 1. Scavenger and potassium formate in a weight ratio in the range of 1:9 to 9:1.

[0051] 2. Preferred ranges for composition 1 include 35-65% scavenger to 65%-35% KCOOH.

[0052] 3. Compositions 1 and 2 may, and preferably will, include water. Preferably, the water will be present in amounts to make solutions of potassium formate in concentrations of 10% to 90% by weight.

[0053] 4. Compositions 1, 2, and/or 3 may include KOH, which may be present as an excess from the reaction of potassium hydroxide with formic acid to make potassium formate.

[0054] The following experiment demonstrates the invention:

EXAMPLE 1

[0055] An aqueous solution was prepared by reacting (a) a molar amount of formaldehyde with (b) a 0.5 molar amount of monoethanolamine and a 0.5 molar amount of amine heads (the molar calculation being based on the nitrogen content. An additional 10% by weight of a 60% by weight solution of potassium formate was introduced, and further diluted with another 15% by weight water. This solution was placed in a treating vessel including a spreader bar. A gas containing varying concentrations of hydrogen sulfide evolving from water separated from a small gas well was bubbled through the solution at a rate of 300-500 scf/day. The hydrogen sulfide was removed from the gas in amounts as high as 12,000 ppm based on the gas.

[0056] In addition to the uses for the invention mentioned above, our invention bay be used to treat drilling fluids, particularly as they are recirculated. 

1. Method of reducing the level of sulfide impurities present in a hydrocarbon or hydrocarbon substrate containing a sulfide comprising contacting the hydrocarbon or hydrocarbon substrate with potassium formate and a sulfide scavenger.
 2. Method of claim 1 wherein said sulfide scavenger comprises a reaction product of an amine and an aldehyde.
 3. Method of reducing the level of sulfide impurities present in a hydrocarbon also containing water comprising (a) contacting said hydrocarbon with potassium formate to extract at least some of said sulfide impurities with at least some of said water from said hydrocarbon and (b) contacting said water with a sulfide scavenger.
 4. Method of claim 3 wherein said potassium formate is in an aqueous solution.
 5. Method of claim 4 wherein said aqueous solution includes potassium hydroxide.
 6. A composition comprising a sulfide scavenger and potassium formate in a weight ratio of 1:9 to 9:1.
 7. Composition of claim 6 wherein said potassium formate is in an aqueous solution.
 8. A composition of claim 7 including potassium hydroxide.
 9. Composition of claim 7 wherein said potassium formate is made by the reaction in water of potassium hydroxide and formic acid.
 10. Composition of claim 8 wherein said potassium hydroxide is in excess of the molar amount for reaction with said formic acid.
 11. Method of scavenging a sulfhydryl compound from a hydrocarbon substrate containing a sulfhydryl compound or an aqueous substrate containing a sulfhydryl compound, comprising contacting said substrate with potassium formate and a sulfide scavenger, said sulfide scavenger comprising an amine/aldehyde condensate.
 12. Method of claim 11 wherein said potassium formate is in aqueous solution.
 13. Method of claim 12 wherein said potassium formate solution contains potassium hydroxide in addition to said potassium formate.
 14. Method of claim 12 wherein said substrate is a hydrocarbon substrate and at least two contactings of said substrate are made.
 15. Method of removing a sulfide from an aqueous sulfide-containing substrate comprising contacting said sulfide-containing composition with potassium formate and a sulfide scavenger.
 16. Method of claim 15 wherein said sulfide-containing composition is a pulp-containing composition in a paper-making facility.
 17. Method of claim 15 wherein said sulfide-containing composition is a sewage composition.
 18. Method of claim 15 wherein said substrate is an aqueous waste stream from a tanning facility
 19. Method of claim 15 wherein said substrate is an aqueous waste stream from a pulp mill.
 20. Method of claim 15 wherein said substrate is a drilling fluid. 